The British eventing trainer gave me a useful sheet with the fitness training regimes. I have got a playlist on my phone and have music tracks of about 2&3 mins set up on it. I play it quietly but out loud as we hack (no headphones!), and we simply trot for a track, walk for a track, trot for two tracks etc building it up.
I'll be really interested to hear if anyone has a proper app for this as it would make things much easier!
No reason why not if you start gently and work up (to avoid injury). I would double the distances/times but keep speeds about the same. Then you will need to adjust slightly for whatever terrain you ride on, and remember, like a human your intervals should only be 10 to 20 percent of your total volume of work (once or twice a week) with lots of slower work too. Good luck!